Well pipe plug



Jan. 24, 1939. F. STONE ET AL WELL PIPE PLUG Filed May 23, 1936 4 Sheets-Sheetl 0 H 5 a \V g WWW W m; ,)f m mfi m v .c e T 1 g F E 70 MM 5 i Z w Z z/ 2 ,9 4v r; l 6 7 w 5 3 3 m 9 mm x z Q Z w Z x w w MN a I 4/ /7 7 .J. r 2 a Jan. 24, 1939. F. STONE ET AL W LL PIPE PLUG Filed May 23, 1936 4 Sheets-Sheet 2 JrweIzZ'v/m Irederwk Stone,

Granville 3127x012 .Hllarnegy.

WM 1 4 5 9. 4. mm m 0 a 9 F 4 4 4 4 Jan. 24, 1939. F. STONE Er AL I WELL PIPE PLUG Filed May 25, 1936 4 Sheets-Sheet Frederztli Stale,

%wille5]fnac llll llllrllllllfl m I pllllllllrlllillllfrll kBlN Jan. 24, 1939. F. STONE ET AL WELL P I PE PLUG Filed May 23, 1936 4 Sheets-Sheet 4 IIZUCIZZOIS Frederick 5 Z0120, Granville 5. 157m flltorrzey.

ll I l n' zm Patented Jan. 24, 1939 Knox, Los Angeles, Calif., assignors to ilydril Company, Los Angeles, Calif., a. corporation of California Application May 23, 1936, Serial No. 81,466

30 Claims.

This invention has to do with plugs for closing well pipes below the ground surface against the upward flow of well fluid, and while certain features of the invention are applicableto such plugs generally, the invention is primarily concerned with an improved type of plug adapted to be forced down within the drill string to facilitate its removal after the occurrence of a twist-off. Accordingly, the invention will be described with that main objective in view.

Occasionally during well drilling operations, the drill string, comprising successive lengths of pipe connected by couplings, becomes severed as a result of torsional or other strains, so that it is necessary to remove the upper severed section from the well and to then recover the lower section. In case the well is flowing gas or liquid, the upper severed section of the drill string is customarily pulled through a packing head on the casing that holds the Well pressure and prevents fluid leakage around the drill pipe. One

of the major objects of the invention is to keep the drill pipe closed against the escape of well fluid therethrough as the pipe is being pulley, by the use of an improved type of plugwhich is pumped or otherwise moved down within the pipe and finally positioned to close the pipe at or near its lower end. In its preferred form, the plug comprises expansible packer and pipe engaging means, both of which are maintained in radially contracted condition as the plug is being pumped downwardly through the pipe, and which are releasable to seal off around the plug and to hold it against subsequent longitudinal movement in the pipe. One of the principal features of the invention is the provision of a control device. whereby the packer and pipe engaging means are automatically caused to expand by virtue of movement of a portion of the plug out of the lower open end of the pipe.

Preferably we provide in the plug a pipe engaging means adapted to arrest plug movement by engagement with an internal shoulder of a flush joint type drill pipe, and in a position such that when set, the packer will be positioned in a re duced diameter coupling bore. In this manner, we are able to avoid having to expand the packer to an extent greater than the minimum internal diameter of the drill string, and yet maintain a fluid-tight closure. As will later appear, the plug has certain dimensional characteristics relative to the pipe stand lengths, that will insure final positioning of the plug at predetermined locations relative to the lower end of the drill pipe.

The invention embodies numerous additional objects and aspects, but all these as well-as the features referred to above will be better understood from the following detailed description of the invention in one of its typical and preferred forms. Throughout the description, reference is had to the accompanying drawings, in which:

Fig. l is a general view, partly in section, showing the plug positioned above the kelly cock and before being released to be pumped down through the drill string} p Fig. 2 is a view similar to Fig. 1 showing the plug released for passage downthroughthe drill string and with the adapter sleeve in engagement with the top'pipe coupling; v

- Fig. 3 is an enlarged fragmentary sectional view illustrating the positions of the latch arms as the plug is being forced v downwardly through the adapter sleeve; 1 v 1 Figs. 4, 5, 6, and 7 are longitudinalsectional views, continuing in downward progression in the order named, showing the plug parts in set position with the latch arms confined by the adapter sleeve;

Figs. 8, 9, 10 and 11 are sectional views similar respectively to Figs. 4, 5, 6 and 7, showing the plug parts in released positions with the packer radially expanded and the pipe gripping means projected radially into the engagement with a coupling shoulder;

Figs. 12 and 13 are vertically continuing views showing the drill pipe in section and the plug in elevation, with its lower end project-ing out the lower end of the upper severed section of the drill string;

Figs. 14 and 15 are enlarged cross sections on lines l4l4 and l5--|5 of Figs. 5 and 9, respectively, showing the pipe engaging balls in radially contracted and expanded positions;

Fig. 16 is an enlarged cross section on line l6-|6 of Fig. 6; and

Fig. 17 is an enlarged cross section takenon line I'l| I of Fig. 7 through the latch arm pivots.

In the drawings we have shown a typical and preferred form of plug, generally indicated at 20 (see Figs. 1, 2, 12 and 13) whose normal diameter is suificientlyv small to enable the plug to pass freely down through the drill string 2 I. The latter is shown typically tobe made up of pipe lengths 22 connected by external flush joint couplings 23, the threaded box ends of the pipe having internal upsets 24 beyond the coupling pin ends 25 which present internal annular shoulders 26 adjacent the pipe upsets. In the specific form of the invention shown, the pipe engaging means carried by the plug is particularly adapted for engagement, when released, with the coupling shoulders 26 to prevent longitudinal movement of the plug within the drill string, and while this type of pipe engaging means is preferred, it is to be understood that the invention is not necessarily limited thereto. For reasons that will later appear, the length of the plug 20 has a predetermined relationship to the length of a complete pipe stand comprising one pipe length 22 and a single coupling 23. As best illustrated in Figs. 12 and 13,

the plug length is in excess of the length of a standard single pipe stand for example, assuming the pipe stand to be around twenty-eight to thirty feet long, the plug length preferably will be greater by at least five or six feet in order to insure that regardless of where the twist-off may occur, the plug will be finally positioned in the desired predetermined position within the pipe above. Incidentally it may be mentioned that ordinarily the twist-offs will occurat points 21 at which the pipe upsets reduce down to the normal 1 thickness .of the pipe.

Referring now to Figs. 4 to 7, the plug 28 may be generally described as comprising a tubular body 28 including a series of pipe sections 29 connected by couplings 30, the number. of these pipe sections and couplings intermediate the uppermost coupling 38a and the lowermost section 29a being determined by the desired length of the plug. For convenience of illustration, Fig. has been broken at 3|, with the understanding that between the portions of the plug above and below the break will be included a number of additional sections 29 and couplings 30. The plug comprises an elongated and radially expansible packer 32 carried on head 33 extending above the upper end of the body 28, and movable longitudinally relative thereto the packer being maintained in radially constricted condition, as shown in Fig. 4, during downward passage of the plug I through the drill string, and finally released for expansion into engagement with the pipe, see Fig. 8, by a spring actuated means generally indicated at 33L The latter is controlled by latch device 34, see Fig. '7, operating to release the packer by movement of the latch out of the lower end of the pipe. When the packer is released, upward movement of the plug within the pipe is arrested by a pipe engaging means generally indicated at 35, which also is actuated by the latch controlled device 33| as the plug is projected out of the lower end of the pipe.

Referring particularly to Fig. 4, the head 33 comprises an enlarged diameter upper end por: tion 33a having a tapered nose 36, an elongated and reduced diameter intermediate portion 33b which tapers down at 37 to a lower rod portion 330 slidably extending'through the bore 38 of a packer constricting fitting 39 threaded into the upper end of the top body section 29. As will later appear, release of the packer for'expansion within the pipe is controlled by relative longitudinal movement between the head and the upper counterbored end 47 of member 39. An elongated packer sleeve 40 of flexible and compressible material, preferably rubber, is formed about the head 33, the upper portion 40a of the packer being set within an annular undercut recess 4| in the head and vulcanized thereto. If desired,-

the packer may be strengthened by suitable reenforcing, as by means of fabric 42 embedded therein. The packer has a substantially uniform external diameter corresponding to or perhaps slightly greater than the outer diameter of the body 28 and top portion 33a'of the head. The lowerportion of the packer below recess 4| is slidable and compressible longitudinally of the head, and is shaped in conformity with the tapered surface 31 of the head and the reduced diameter portion 330 therebelow.

The lower end of the packer sleeve is annularly split as indicated at 44 to provide lips 45 and 46 adapted to be forced by upwardly applied fiuid pressure, into fluid-tight engagement with the drill pipe 2| and portion 330 of the head, respectively. Normally the lower lipped end of the packer is radially constricted and confined against expansion by an extension 41 on the upper end of member 39, having a tapered bore 48 and one or more openings at 49. The packer is held within bore 48 and prevented from accidental withdrawal, by means of a coil spring 50 confined between the lower pin end of fitting 39 and nut 5| on the lower end of portion 330 of the head depending within the body 28. Normally, nut 5| engages the upper end of coupling pin 52 to limit downward movement of the head relative to the body. Upward relative movement of the head is limited by the engagement of stop sleeve 53 with the lower end of pin 54, as shown in Fig. 9, after the lower end of the packer has been withdrawn from the tapered bore 48. Before the plug is put into the pipe string, the lower lip portions 45 and 46 are securely tucked within the tapered constrictor 31, in the condition shown in Fig. 4.

The packer releasing device 33| comprises an elongated rod assembly made up of sections 56 threadedly connected by couplingsleeves 51 engaged by lock nuts 58, Rod section 56a has a threaded connection at 59 with the upper end of a pair of rod lengths 60 connected at 6| and carrying two longitudinally spaced sets of circularly spaced lugs 62 engaged by coil springs 63 and 84, the upper spring being supported on the internal body flange 65 and the lower spring on the upper end-of pin 66. Springs 63 and 64 normally are compressed and the rod assembly releasably held in depressed position. within the body, by the latch mechanism 34. The latter comprises a lower tubular body section 61 having intermediate its ends a pair of elongated and diametrically opposed slots 68, and closed at its lower end by a tapered nose 69 having a bore 18 normally closed by cap screw 1|. Section 61 contains below slots 68 a rebound check device in the form of a tubular member 12 that is clamped between pin 13 and shoulder 14 by taking up the joint at 15, and having a pair of upwardly projecting spring fingers 16 that are normally spread to receive the lowermost rod section 17 in the position of Fig. 7. When the rod is raised, as will presently appear, spring fingers 16 move together in the position of Fig.

. 11 to prevent possible rebound of the rod to the point of again entering between the fingers.

Lower rod section 11 is connected at 18 with the rod length 60 above, and has a portion Ila of rectangular cross section within opposite sides of which are formed notches |9 which receive lugs 80 on a pair of latch arms 8| pivoted for vertical swinging'movement on pins 82, see Fig.

17, terminating within body portion 61 at opposite sides of slot 68. When the plug is assembled for insertion within the drill string, latch arms 3| are held in the position of Fig. 7 to retain the rod assembly in set or depressed position, by an adapter sleeve 83 placed around the lower end of the plug and having at its upper end an angular surface shoulder 84 which is engaged by the notched portions 8|a of the latch arms. The internal diameter of the adapter sleeve 83 is sliglitly larger than the plug outside diameter, so that when downward movement of the adapter is arrested under the conditions later explained, the

86, see Fig. 14, extending radially outward from the bore 81 of coupling 38a, and containing balls 88 adapted to be projected outwardly to the expanded position of Fig. 15, beyond which the balls are prevented from moving by slight constrictions 89 at the ends of openings 86. As the plug is being pumped down through the drill string, balls 88 assume the retracted positions of Figs. 5 and 14. When the rod assembly 33 is released by latch 34 for upward travel within the body, balls 88 are projected outwardly to their expanded positions by the action of rod extension 90' having a tapered cam surface 9| adapted, upon upward movement, toengage and spread the balls.

While the plug may be inserted within the drill string in any suitable manner, Figs. 1 and 2 will illustrate a typical sequence of. operations for introducing the plug. In Fig. 2 the drill string 2| is shown to extend upwardly through a conventionally illustrated packing head 92 on the casing 93, and to be connected by coupling 84 with the usual kelly 95. The drill string is supported by slip bushings 98 within the diametrically illustrated table 91, and the upper end of the kelly carries the usual cock 98 below the swivel 99 through which circulating fluid is discharged downwardly through the pipe string, when cook 98 is open, from the rotary hose I00 via gooseneck Hll about the swivel.

In preparation for pumping the plug down through the drill string, the plug 20 is inserted throughthe swivel 99 and rested on top of cock 98 with the latter in closed position. A pipe I02, closed at its upper end by cap I83, is lowered over the plug and threaded at I04 into the upper end of the gooseneck. Cock 98 then is opened and circulating fluid pumped through line I09 to force the plug downwardly into the pipe string 2|. As previously mentioned, the adapter sleeve 83 first will have been slipped over the lower end of the plug to hold the latch arms or dogs 8| in set position, and the bottom lipped end of the packing rubber tucked within the tapered bore 48 of the constricting member 41. If these prep arations are not made, the plug will not pass through the tool joints of the pipe string. When the plug is forced down to the position of Fig. 2, adapter sleeve 83 is arrested by engagement with the internal shoulder I95 of coupling 94 as shown in Fig. 3. The plug however is forced on down through the adapter, causing arms 8| to be swung inward and thereafter released within the drill pipe to the maximum outer positions (when between couplings) shown in dotted lines, but confined sufficiently while in the drill pipe, to hold the rod assembly in depressed position.

The plug is forced on down through the pipe until its lower end passes out the open end I08 of the pipe which, as shown in Fig. 13, is the location of the twist-off; The lower severed section of. the drill string is indicated at I91. When the nose of the plug passes out of the end I08 of the pipe, latch arms 8| are thrown out of engagement with the latch rod, and swung outwardly and downwardly to the released positions of Fig. 11. Immediately upon release of the latch, springs 63 and 64 project the latch rod upwardly into engagement with balls 88, displacing them outwardly, see Figs. 8 to 11, and engaging the lower end of the head 330 to elevate it to the position of Fig. 8 and withdraw the packer from bore 48. Inraising the head 33 relative to the body, springs 63 and 64 of course overcome the resistance of spring 5!]. Continued movement of the plug out of the drill pipe is prevented by the engagement of balls 88 with coupling shoulder 29, which engagement is indicated at the ground surface by a quick rise in the circulating fluid pressure. The pumps then are quickly stopped and the circulating fluid pressure slowly released to allow a moderate upward flow of well fluid. This upward flow carries the plug upwardly to bring the packer within the bore of coupling 23a in a position predetermined by the engagement of balls 88 with the lower end of the coupling pin as shown in Figs. 8 and 9. The well pressure effectively expands the packer lip into fluid tight engagement with the coupling bore, preventing further upward flow of fluid.

Fig. 8 illustrates successive positions of the lower portion of the packer during travel of the head 33 as it is projected upwardly by a rod assembly 33| when the latter is released by the latch. As will be understood from the foregoing,

ing means 41, the packer 48 will be positioned within the relatively large diameter pipe bore below the coupling 23, in which position the lower lipped end of the packer will have expanded to substantially the dotted line position shown in Fig. 8. Then, as the packer is moved upwardly into the coupling bore 23l, the packer is forced by the well fluid pressure into fluid-tight engagement with the coupling, the well pressure acting to force lip outwardly against the coupling bore and to constrictlips 46 about portion 330 of the head, and also to longitudinally compress the lower portion of the packer, i. e., below recess 4|, by upward movement relative to the mandrel portions 33b and 330 of the head. As the packer is forced upwardly relative to the mandrel it is expanded into tight engagement within the coupling bore, both by the inherent expansibility of the rubber upon compression, and by the effect of the mandrel taper 31 to spread the rubber.

By reference to Figs. 12 and 13 it will be seen that with the twist-off occurring directly below coupling 23b, the packer 32 will be set within the bore of. coupling 23a spaced two pipe lengths f above, with the balls 88 in engagement with the bottom shoulder of that coupling. As will be readily seen without the necessity for specific illustration, should the twist-off occur directly above the coupling (not shown) immediately below coupling 23b, then after the latch has been released and the plug moved upwardly by the well pressure, packer 32 will seat within and balls 88 engage the bottom end 28 of coupling 23.

For the purpose of resetting the plug, it is necessary to remove cap screw II in the nose of section 61, thread a resetting tool or rod into bore H0, see Fig. 11, and pull down the rod assembly until lugs 80 of the latch arms 8| reenter notches 19. Upon further downward movement of the resetting tool and rod assembly, the latch arms will fold inwardly into the body slots, and the adapter sleeve may then he slipped over the arms to retain them in the set position. After resetting, lip 45 of the packer is again tucked into counterbore 48 of the constricting member 41.

In the foregoing description, we have referred to the plug as being operated by movement out of the lower open end of a severed pipe. It will of course be understood that the utility and operativeness of the plug are not limited to situations where a pipe happens to be severed, as at a twist off, and that the plug may be caused to operate automatically upon movement out of the lower end of any pipe below which there is sufiicient space for the latch arms 8i to swing outwardly to the extent of releasing the rod assembly.

We claim:

1. In a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, control means maintaining said packer in radially constricted condition during the downward passage of the plug in said pipe, the last mentioned means comprising a member movable vertically within the plug, a spring tending to move said member to cause the packer to expand within said pipe, and means for releasably holding said member against movement by the spring, the last mentioned means being releasable by movement of a lower portion of the plug out of the lower end of the pipe.

2. A plug adapted to be moved downwardly through a well pipe that is open at its lower end, said plug comprising radially movable means adapted to engage the inside of said pipe to hold the plug against upward movement therein, a member movable longitudinally within said plug to expand said pipe engaging means, a spring for so moving said member, means for releasably holding said member against movement by the spring, the last mentioned means comprising a latch operating by movement out of the lower end of said pipe to release said member for movement by said spring, and a packer having a depending lip portion expansible into tight engagement with the well pipe by upwardly applied fluid pressure.

3. In a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, control means maintaining said packer in radially constricted condition during downward passage of the plug in said pipe, radially movable means adapted to engage the inside of said pipe to hold the plug against upward movement therein, and means responsive to move ment of a lower portion of said plug out of the lower end of the pipe, for actuating both said packer control means and pipe engaging means to expand them within said pipe at points spaced above its lower end.

4. In. a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, control means maintaining said packer in a radially constricted condition during downward passage of the plug in said pipe, radially movable means adapted to engage the inside of said pipe to hold the plug against upward movement therein, and means responsive to movement of a lower portion of said plug out of the lower end of the pipe, for actuating both said packer control means and pipe engaging means to expand them within said pipe at points spaced above its lower end, the last mentioned means comprising a member movable vertically within the plug, a spring tending to move said member to cause the packer and pipe engaging means to expand within said pipe, and means for releasably holding said member against movement by the spring, the last mentioned means being releasable by movement of a lower portion of the plug out of the lower end of the pipe.

5. In a well pipe plug adapted to be forced downwardly through the pipe by fluid pressure, an elongated tubular body, a packer adapted to be radially expanded into fluid tight engagement with said pipe, means controlling the expansibility of said packer, pipe engaging means adapted to be moved radially outward relative to said body, and an elongated rod movable longitudinally within said body to actuate both said packer control means and said pipe engaging means.

6. In a well pipe plug adapted to be forced downwardly through the pipe by fluid pressure, an elongated tubular body, a packer adapted to be radially expanded into fluid tight engagement with said pipe, means controlling the expansibility of said packer, pipe engaging means adapted to be moved radially outward relative to said body, and an elongated rod movable upwardly within said body from depressed to projected position to actuate both said packer control means and said pipe engaging means, a spring tending to thrustsaid rod upwardly, and means for releasably holding said rod in its depressed position.

7. In a well pipe plug adapted to be forced downwardly through the pipe by fluid pressure, an elongated tubular body, a packer adapted to be radially expanded into fluid tight engagement with said pipe, means controlling the expansibility of said packer, pipe engaging means adapted to be moved radially outward relative to said body, and an elongated rod movable upwardly within said body from depressed to projected positions to actuate both said packer control means and said pipe engaging means, a spring tending to thrust said rod upwardly, and a latch releasably holding said rod in depressed position,

said latch being releasable by movement out of the lower end of said pipe.

8. In a well pipe plug adapted to be forced downwardly through the pipe by fluid pressure, a tubular body, a packer adapted to be radially expanded into fluid tight engagement with said pipe, and pipe engaging balls adapted to be moved radially outward Within openings in said body into engaging position with said pipe to hold the plug against longitudinal movement therein.

9. In a well pipe plug adapted to be forced downwardly through the pipe by fluid pressure, an elongated tubular body, a packer adapted to be radially expanded into fluid tight engagement with said pipe, means controlling the expansibility of said packer and comprising a member normally surrounding and confining an expansible portion of said packer but movable relative to the packer to release said portion for expansion, pipe engaging means adapted to be moved radially outward relative to said body, and an elongated rod movable longitudinally within said body to actuate both said packer control means and said pipe engaging means.

10. In a well pipe plug adapted to be forced downwardly within the pipe by fluid pressure, the combination comprising a radially expansible packer, a member having a bore receiving and holding one end of said packer in radially constricted condition, said member being movable relative to said packer to release said end of the packer from said bore to permit expansion of said end, and means for so moving said member after the plug has been forced down into the well pipe and is unsupported from the ground surface excepting whateversupport may be given the plug by engagement with said pipe.

11. In awell pipe plug adapted to be forced downwardly within the pipe by fluid pressure, the combination comprising a radially expansible packer, a member having a bore receiving and holding one end of said packer in radially constricted condition, yielding means urging said member into engagement with the packer, said member being movable relative to said packer to release said end of the packer from said bore to permit expansion of said end, and means for so moving said member after the plug has been forced down into the well pipe and is unsupported from the ground surface execepting whatever support may be given the plug by engagement with said pipe.

12. In combination with a well pipe string comprising joined pipe sections and having downwardly facing internal shoulders at the joints, a plug adapted to be forced downwardly through the pipe string, a packer carried by the plug, pipe engaging means carried by said plug and movable from radially contracted to expanded positions, and means for positively expanding said pipe engaging means to arrest movement of the plug longitudinally within the pipe string, said plug being movable upwardly from any point between successive pipe joints and with said pipe engaging means in expanded position until the pipe engaging means engages the internal pipe string shoulder immediately above said engaging means.

13. In combination with a well pipe string comprising joined pipe sections and having downwardly facing internal shoulders at the joints, a plug adapted to be forced downwardly through the pipe string, a packer carried by the plug, pipe engaging means carried by said plug and movable from radially contracted to expanded positions, and means for expanding said pipe engaging means to arrest movement of the plug longitudinally within the pipe string, by virtue of movement of a lower portion of said plug out of the lower end of the pipe, said plug being movable upwardly from any point between successive pipe joints and with said pipe engaging means in expanded position until the pipe engaging means engages the internal pipe string shoulder immediately above said engaging means.

14. In combination with a well pipe string comprising joined standard pipe sections and having downwardly facing internal shoulders at the joints, a plug adapted to be forced downwardly through the pipe string, a pa'cker carried by the plug, the length of said plug below the packer being in excess of the length of one of said pipe sections, pipe engaging means carried by said plug and movable from radially contracted to ex panded positions, and means for expanding said pipe engaging means to arrest movement ofrthe plug longitudinally within the pipe string, by "irtue of movement of a lower portion of said plug out of the lower end of the pipe, said plug being movable upwardly from any point between successive pipe'joints and jith said pipe engaging means in expanded position until the pipe engaging means engages the internal shoulder immediately above said engaging means.

15. In combination with a well pipe string comprising a series of pipe stands each consisting of a pipe section connected at its upper end with a coupling having a reduced diameter bore and presenting within the pipe string a downwardly facing shoulder, a plug adapted to be forced downwardly within the pipe string, a packer carried by said plug, said packer being adapted to be inserted within the bore of one of said couplings by upward movement of the plug in the pipe string, and then to be expanded by the well pressure into fluid tight engagement with the coupling, and radially expansible means carried by the plug and adapted to engage the lower end of said packer receiving coupling to prevent further upward movement of the plug.

coupling having a reduced diameter bore and presenting within the pipe string a downwardly facing shoulder, a plug adapted to be forced downwardly within the pipe string, a packer carried by said plug, said packer being adapted to be inserted within the bore of one of said couplings by upward movement of the plug in the pipe string, and then to be expanded by the well pressure into fluid tight engagement with the coupling, and radially expansible pipe engaging means carried by said plug and adapted to engage the lower end of said packer containing coupling to prevent further upward movement of the plug.

1'7. In combination with a well pipe string comprising a series of pipe stands each consisting of pipe section connected at its upper end with a coupling having a reduced diameter bore and presenting within the pipe string a downwardly facing shoulder, a plug adapted to be forced downwardly within the pipe string, a packer carried by said plug, releasable means acting normally to radially constrict said packer, said packer being adapted to be inserted within the bore of one of said couplings by upward movement of the plug in the pipe string and then to be expanded by the well pressure into fluid tight engagement with the coupling, and means for releasing said packer constricting means by virtue of movement of a lower portion of said plug out of the lower end of said pipe.

18. In combination with a well pipe string comprising a series of pipe stands each consisting of a pipe section connected at its upper end with a coupling having a reduced diameter bore and presenting within the pipe string a downwardly facing shoulder, a plug adapted to be forced downwardly within the pipe string, a packer carried by said plug, said packer being adapted to be inserted within the bore of one of said couplings by upward movement of the plug in the pipe string, and then to be expanded by the well pressure into fluid tight engagement with the coupling, radially expansible pipe engaging means carried by said plug and adapted to engage the lower end of said packer containing coupling to prevent further upward movement of the plug, and means for actuating saidpipe engaging means by virtue of movement of a lower portion of said plug out of the lower end of said pipe.

19. In combination with a well pipe string comprising a series of pipe stands each consisting of a pipe section connected at its upper end with a coupling having a reduced diameter bore and presenting within the pipe string a downwardly facing shoulder, a plug adapted to be forced downwardly within the pipe string by fluid pressure, a packer carried by said plug,'releasable means acting normally to radially constrict said packer, said packer being adapted to be inserted within the bore of one of said couplings by upward movement of the plug in the pipe string and then to be expanded by the well pressure into fluid tight engagement with the coupling, and means for releasing said packer constricting means by virtue of movement of a lower portion of said plug out of the lower end of said pipe, the length of said plug below the packer being in excess of the length of one of said pipe stands.

20. In combination with well tubing comprising pipe sections connected by a coupling forming at its lower end a downwardly facing shoulder and having a bore smaller than the pipe bore, a plug comprising a radially expansible packer, radially expansible pipe engaging means directly below the packer and movable downwardly through the coupling bore, and means for positively expanding said pipe engaging means, the pipe engaging means being adapted to engage the lower end of the coupling with said packer inserted in the packing bore above, to arrest upward movement of the plug.

21. In combination with well tubing comprising pipe sections connected by a coupling forming at its lower end a downwardly facing shoulder and having a bore smaller than the pipe bore, a plug comprising a mandrel, a packer sleeve surrounding the mandrel and expansible by movement longitudinally thereof, radially expansible pipe engaging means directly below the packer and movable downwardly through the coupling bore, and means for positively expanding said pipe engaging means, the pipe engaging means being adapted to engage the lower end of the coupling with said packer inserted in the packing bore above, to arrest upward movement of the plug.

22. A well pipe plug comprising a body, radially expansible pipe engaging means carried by the body, a radially expansible packer mounted on the body, means for controlling the expansion of said pipe engaging means, and a sleeve surrounding the body and releasably holding the last mentioned means against movement to cause the pipe engaging means to expand, said plug being downwardly movable through and separable from the sleeve to release said control means.

23. A well pipe plug comprising a body, radially expansible pipe engaging means carried by the body, a radially expansible packer mounted on the body, means for radially expanding said pipe engaging means, and a sleeve surrounding the body and releasably holding the last mentioned means against movement to expand the pipe engaging means, said body and the packer and pipe engaging means being movable downwardly through and out of said sleeve to release the pipe engaging means for expansion and to free the plug from the sleeve.

24. In a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, control means maintaining said packer in radially constricted condition during downward passage of the plug in said pipe, and means located at a lower portion of the plug and controlled by engagement with the pipe, the last mentioned means operating upon its movement out of the lower end of the pipe, to actuate said packer control means to cause said packer to expand within said pipe at a point above its lower end.

25. In a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, means for releasably holding said packer in radially constricted condition during downward passage of the plug in said pipe, and means normally engaging the pipe and actuated by virtue of its movement out of the lower end of the pipe, for releasing said holding means to permit the packer to expand radially within the pipe.

26. In a plug adapted to be moved downwardly through a well pipe, a packer adapted to be expanded radially into fluid tight engagement with said pipe, control means maintaining said packer in radially constricted condition during downward passage of the plug in said pipe, and means including a latch device carried by the plug below the packer and operable by movement out of the lower end of the pipe to actuate said packer control means and to cause the packer to expand within said pipe at a point above its lower end.

27. A plug adapted to be moved downwardly through a well pipe that is open at its lower end, said plug comprising radially movable means adapted to engage the inside of said pipe to hold the plug against upward movement therein, means normally engaging the pipe and actuated by virtueof movement out of the lower end of the pipe, for radially expanding said holding means within the pipe at a point above its lower end, and a packer having a depending lip portion expansible into tight engagement with the well pipe by upwardly applied fluid pressure.

28. A plug adapted to be moved downwardly through a well pipe that is open at its lower end, said plug comprising radially movable means adapted to engage the inside of said pipe to hold the plug against upward movement therein, means for radially expanding said engaging means Within the pipe at a point above its lower end, the last mentioned means comprising a member movable relative to said pipe engaging means, and normally engaging the pipe and located at the lower portion of the plug, the last mentioned means being operable by movement out of the lower end of the pipe to expand the pipe engaging means, and a packer having a depend ing lip portion expansible into tight engagement with the well pipe by upwardly applied fluid pressure.

29. A well pipe plug adapted to be dropped or forced downwardly by fluid pressure within a well pipe, said plug including a body, radially expans'ible pipe engaging means carried by the body, yielding means for expanding said pipe engaging means, holding means for releasably maintaining said pipe engaging means in contracted position when the pipe engaging means is out of the pipe, and control means normally engaging the pipe bore wall and operable by movement out of the lower end of the pipe to expand said pipe engaging means within the pipe, said holding means being releasable after the pipe engaging means is inserted within the pipe to permit expansion of the pipe engaging means upon movement of the control means out of the lower end of the pipe.

30. A well pipe plug adapted to be dropped or forced downwardly by fluid pressure within a well pipe, said plug including a body, a radially expansible packer carried by the body, means for expanding the packer, holding means for releasably maintaining the packer in contracted condition when the pipe engaging means is out of the pipe, and control means normally engaging the pipe bore wall and operable by movement out of the lower end of the pipe to release said packer for radial expansion within the pipe, said holding means being releasable after the packer is inserted within the pipe to permit expansion of the packer upon movement of the control means out of, the lower end of the pipe.

FREDERICK STONE. GRANVILLE S. KNOX. 

